Except the friend doesn't seem to get why she has been rude, won't take no for an answer and has now got her sister to email Tidy to say she is "upset."

I don't know what your settings on MN are like but mine show the OP's posts as green. If you have that I'd suggest skimming through and just reading Tidy's posts which have the texts of the emails on them. And then join us all in breathless outrage . . .

Oh yeah, the sister is getting a rundown of the facts and that's it. I'm not going to say I'm upset or anything like that, I think I just need to let her know exactly what's happened.

I do wonder if she suspects bridezilla is being bridezilla-ish as she hasn't accused me of anything, she has just requested to know what is going in as her sister is upset about it. It didn't come across as having a tone about it. It makes me think that perhaps I'm not the only one who has been subjected to some unreasonableness during this wedding!

Sorry to hear your sister is upset, however I am confused as to why.I made it very clear from the outset that I was not available to decorate her wedding venue. I had booked the day off when I received a save the date card as was under the impression I was invited to the wedding itself.However when your sister told me I wasn't invited (totally her prerogative), I cancelled my day off for a time when I needed it.It was only after she told me I was not invited she asked me to decorate. I am sure you appreciate that this was rather impolite especially as I would have to give up one of my days off and pay for childcare.I wish you luck helping her find an alternative decorator. As far as I am concerned the matter is closed.I really do hope she has a lovely day.

I agree, OP, just a very factual email, and hopefully that will put an end to it. I cannot believe the bride's cheek, I think it is safe to say your friendship is over. You have been very dignified throughout. I am guessing that the bride's sister was given a very different version of the story.